1. Field of the Invention
The present invention concerns a foam spring, in particular a foam spring with a tubular resilient body made of foam with holes extending inwardly from the outside and which can be applied in the core of pillows, mattresses, armchair cushions or the like.
The invention also concerns a method of manufacturing such a foam spring.
2. Discussion of the Related Art
Such foam springs are known, for example, from U.S. Published Patent Application No. 2005/172468 and European Patent Document No. 0 872 198, disclosing a foam spring made of a foam layer strip of, for example, latex or polyurethane foam, provided with slits, whereby the strip is bent and two opposite ends of the strip are glued together to form a hollow tubular body with diamond shaped holes formed by stretching the slits in a lateral direction due to the bending of the strip.
Although known foam springs are very much valued by the users of the pillows, mattresses or the like, they have a disadvantage that they are not suitable for use by persons with varying weights.
For example, when a mattress is provided with foam springs having a very low stiffness, such a mattress will be soft and will probably be suitable for a person which is not heavy.
However, when the same mattress is used by a heavy person, the mattress is expected to compress too much so that the person will sink into the mattress and is actually supported by the harder surfaces underneath the mattress, such as the wooden structures of a bed, etc.
A heavier person would therefore use a firmer mattress and a lighter person a softer mattress, but it is not always realizable to adapt the mattress to the person who will use it, as for example in hotels, etc.
Another example is that of a mattress of a double bedstead, which is aimed to be used by two persons at the same time, who usually have a different weight.
If such a mattress is equipped with the known foam springs, the compression of the mattress is often considerably greater at the side of the heaviest person, causing discomfort.
Another drawback of the known foam springs is that the required stiffness of the spring determines a person's feeling at the contact surface with the spring.
In other words, a spring that compresses easily results in a soft contact surface feeling, while a spring that is more stiff will result in a harder contact surface feeling.
However, in some more dynamic situations a spring is required that is very soft in order to absorb and damp certain vibrations, while it is better for the comfort of the user to have a rather hard contact surface, as for example in mattresses and cushions used in certain vehicles.